Beat-frequency heterodyne receiver arrangement



Aus. 18, 1931. s. I QEwE 1,819,609

BEAT FREQUENCY HETERODYNE RECEIVER ARRANGEMENT Filed Nov. 5, 1926 IIUIIIHLIIIHIU Irall!) Yrrlrmfmnnnru imm ,g I y PQI-1 m |11 u null h n L; i 'i LEU @Z22/elder:

Patented Aug. 18, 1931 UNITED STATES PATENT OFFICE SIEGMUND LOEWE, OF FRIEDENAU, BERLIN, GERMANY, ASSIGNOR T0 RADIO CORPORA- TION OF AMERICA, A CORPORATION OF DELAWARE BEAT-FREQUENCY HETERODYNE RECEIVER ARRANGEMENT Application tiled November 3, 1926, Serial No. 146,042, and in Germany November 4, 1925.

10 sent if the other wave were used. Beat-frequency or heterodyne receivers which are to be calibrated on the other hand, are in need of a clear and distinct arrangement of the waves designations and the oscillations of the local oscillator. If only one of the two cases of producing the beat frequency is utilized, distinct calibration is possible, the local oscillator being provided with a wave or frequency designation or scale which from the outset differs by the amount of the prearranged beat frequency from the frequencies actually produced by the local oscillator. But if such a calibration is to be provided both for the higher as weli as for the lower tuning of the local oscillator, then double calibration would be required, that is to say, a calibration for the higher and another one for the lower tuning. Such a calibration arrangement is inconvenient and according to the present invention it is avoided in the following manner.

In both the input circuit and the oscillation circuit of the local oscillator, variable tuning condensers are used of the kind 1n which there exists a linear interdependence between the frequency and the angle of rotation of the condenser, for example equal angular rotational movements of .these condensers produce the same change in the frequency to which the respective circuits are tuned. The adjustment of the i two condensers, if inter-coupled by positive means, results in a constant beat frequency. Furthermore, the same property can be preserved if one of the said two condensers is displaced with reference to the other one by an angle which is equal to twice the beat frequency in which case it 1s referable to have identical condensers in bot circuits. In this position the two condensers can also be coupled by positive means whereby a constant fre uency difference is obtained when the con ensers are simultaneously adjusted.

The operation of the arrangement is as follows. The condenser of the input circuit is positively coupled with the condenser of the local oscillator in such a manner that a relative shifting of the latter with reference to the tuning condenser of the input circuit by twice the amount of the beat frequency is possible. Together with the change from the higher to the lower beat frequency, there occurs a change-over of the scale, indeed, the same is likewise turned by the same constant angle, the latter corresponding to the constant aneular displacement of the two tuning condensers with relation to each other. For instance, when the tuning condenser of the input circuit is set at 90 degrees, the angle of rotation of the similarly formed oscillator or heterodyne condenser may, for the sake of argument, amount to 100 degrees for the production of the lower beat frequency, whereas for the production of the higher beat frequency, it must be set to 80 degrees. In both terminal positions, the two tuning condensers are coupled with each other by positive means, and are turned. The calibration scale itself, however, on changing from the upper to the other frequency is like- Wise turned, in the example, here assumed, by an angle of 20 degrees. In this manner, the calibration provided is preserved accurate, and all that is then necessary is one adjustment for both beat frequencies.

Referring to the drawings:

Fig. 1 is a view partl in section of one form of my invention w ereby two condensers may be simultaneously7 and continuously rotated by means of a common control member, with means for maintaining the rotatable elements of each condenser in two angularly dierent positions relative to each other;

Figs. 2 and 3 are elevational views of members f and d of Fig. 1;

Figs. and 5 diagrammatically show the positions of the control members of Fig. 1 at different settings;

Fig. 6 is a sectional view of another emf bodiment of my invention having in effect a relatively movable scale; and

Fig. 7 is a frontelevation view of the control members of Fig. 6 partly in section.

Turning to Fig. 1, a indicates a condenser for use in the oscillator circuit of, for example, a superheterodyne radio receiving circuit. The rotatable member of this condenser is as shown fastened to shaft c which in turn has fastened at its outer end by a set screw, a control member or knob d. Condenser b is adapted to be inserted in the tuned input circuit of a superheterodyne radio receiving circuit. Both condensers b and a arepreferably of the straight line frequency type.

The rotatable plates of the rotatable element of condenser b are fastened by means `of a suitable set screw to hollow shaft or sleeve e which in turn is adapted to be rotated by a common control member or knob f fixed thereto by, as shown, a set screw.

Knob f has a suitable pointer or indicator g thereon cooperating with a scale h fixed to the front of the receiver. Knob d carries spring compressed means thereon, namely, a plunger i adapted to be forced by .means of a small spring into engagement with holes k on the knob f.

In operation the rotatable elements of condensers a and b are set angularly apart so that the combination of the outputs of the circuits to which they are tuned has the requisite beat frequency. The holes k are angularly spaced apart so that'depending upon the hole into which the plunger member z' is inserted the oscillator circuit in which the condenser ais included will be either above or below the fresuency to which the circuit in which condenser b is included is tuned. The elements should be arranged so that regardless of the hole in which plunger i is placed the difference in frequency between the oscillator and input circuit is constant and equals the desired beat frequency.

The change-over of the plunger or pin z' from one depressioni@ into the other is very easily accomplished if stops are provided for the rotary condenser b connected with knob f, the said stops allowing only of the rotation of the condenser through an angle of 180 degrees in one direction or the other.

Figs. 4 and 5 illustrate such an arrangement. For instance, if the yielding pin just happens to be loca-ted in the depression k1 (Fig. 4) then both operating kno s are capable of being turned to the left-hand side only to a point Where the rotary condenser strikes against its stop. If an attempt'is then made to turn the operating knob d still further towards the left-hand side by the application of a stronger torque, the yielding pin will be caused to disengage and be released from the depression k1 and will en age in the depression 102 because of the kno d then rotatingalone. In this manner, uncoupling of the two operating knobs and thereby also changeover of coupling between the two rotaryn condenser spindles is effected.

Reverse coupling, that is to say, restoration of the yieldin pin from depression k2 into depression k1 is accomplished by the aid of the operating knob d as shown in Fig. 5. Both rotary condensers are turned towards the right-hand side until the rotary condenser b reaches the corresponding stop, when the torque being much reinforced the yielding pin snaps out of the depression k2.

According to the invent-ion. both of the rotary condensers are supposed to be of straight-line frequency type, and they are used in combination with a receiver in the way hereinbefore described. The angle of rotation corresponding to the two depressions k1 and k2 of the rotary condenser b in the oscillation circuit of the oscillator must moreover be so chosen that by means of such angle of rotation the tuning of the said oscillation circuit is varied by the double amount of intermediate frequency which is to be used in the transposition receiver.

In the light of what precedes, the hand of the operating knob f allows of reading on the scale L the incoming frequency or wavelength of the input circuit of the receiver.

Where it is desired to make use of separately controlled condensers in the oscillatorand input circuit as, for example, in a superhetem odyne receiving circuit the oscillator condenser arrangement shown in Figs. 6 and 7 inay be utilized. The input tuning condenser is not shown but is independently actuated.

As in Fig. 1 the oscillator condenser is actuated by a knob d. Knob f, however, is independent-ly arranged on sleeve e and is actuated by the rotation of pinion p cooperating 05 with rack g. Pinion p is rotated by means of knob m and driving shaft n.

In operation, the tuning condenser in the input circuit is first tuned to a desired station. Knob d is then rotated which when it obtains an extreme position relative to knob f will cause knob f to rotate with it. When the correct beat frequency is obtained the signal will be heard very distinctly, the=indica tor on knob f pointing to a definite reading on l5 the station scale h. If at that oscillator tuning there should be heard an interfering stan tion, knob m should be turned so that knob f will be rotated to its other extreme position relative to knob d. The last mentioned rotation of f should represent the angle through which d would have to be turned in order to change the oscillator frequency by a frequency double the beat frequency. From this it is clear that to obtain the other oscillator frequency for cooperating with the input frequency knobs d and f should be rotated together after the last mentioned rotation of f so that f has its original reading on scale h.

Having described my invention what I claim is:

1. In a condenser arrangement for heterodyne radio signalling apparatus, a pair of condensers, a shaft for rotating the movable 1 plates of one of said condensers, a sleeve, for

rotating the movable lates of another condenser, fitting over said shaft, a knob fixed to said sleeve, another knob fixed to said shaft and spring pressed means for Ipositively and selectively locking said knobs together and maintaining the movable plates of said condensers at a desired fixed angular difference.

2. In a condenser arrangement for heterodyne radio signalling apparatus, a pair of condensers, a shaft for rotating the movable plates of one of said condensers, a sleeve, for rotating the movable lates of another condenser, fitting over said shaft, ak knob fixed to said sleeve, another knob fixed to said shaft, a spring pressed plunger in one knob, adapted to cooperate with openings in the other knob for positively maintaining the rotatable elements of said condensers at a fixed angular difference and for allowing of the rotation of both of said rotatable elements by the manipulation of one knob.

3. A radio tuning device comprising a lurality of tuning members, a plurality o independently rotatable, telescoped shafts affixed to the movable elements of said members, an operating knob afiixed to each shaft, and resilient means, mechanically coupling said knobs, for positively and selectively locking the knobs together and maintaining the movable elements of said members at a. desired fixed angular difference.

4. A radio tuning device comprising a pair of condensers, a pair of independently rotatable, telescoped shafts afiixed to the rotors of said condensers, an operating knob affixed to each shaft, means mechanically couplin the knobs, for posltively locking the kno s together whereby said rotors are fixedl maintained in a single desired angular relation during variation of the condensers, and additional means, provided on one of the knobs, for fixedly maintaining the rotors in another angular relation during variation of the condensers.

I EGMUND LOEWE. 

